Thermoplastic materials are used in a variety of industrial applications that include adhesive dispensing and heat sealing applications. Thermoplastic material is processed to produce, among numerous other products, diapers, shrink wrap packages, sanitary napkins and surgical drapes. The technology has evolved from the application of linear beads, or fibers of material and other spray patterns, to air assisted applications, such as spiral and melt-blown depositions of fibrous material.
A number of these and other industrial applications involve stringent regulation and maintenance of system temperatures to mitigate occurrences of over or under heating. Unregulated temperatures can lead to ineffective viscosities, wasted product and/or damaged equipment. In the extrusion of plastics, for example, heated thermoplastic material is conveyed through a suitable conduit to an extruder, and in hot melt adhesive dispensing systems, molten adhesive is conveyed from an adhesive reservoir to a dispenser. Heat sealing operations use crimping bars that seal longitudinal edges of mating thermoplastic film ends. In the case of shrink wrapping, a thermoplastic film is wrapped in tubular form about an article, which passes through a heated shrink tunnel where the thermoplastic film is shrunk around the article.
To monitor temperatures of the equipment and products within these and other thermoplastic applications, it is often desirable to position one or more sensors throughout the system. For instance, a temperature sensor may be positioned within a hot melt dispensing system to provide that a hose is maintained at a desired temperature, e.g., a temperature sufficient to maintain the adhesive in a molten condition as it flows between the reservoir manifold and the dispensers. The same is also true for the dispensers, manifold, and reservoir.
It is also desirable for related reasons to determine if the temperature sensors are open-circuited or short-circuited. Left uncorrected, undetected and/or unregulated temperatures resulting from a failed sensor will cause wasted product, as well as malfunctioning or damaged equipment. As a consequence, systems typically shut down production after a sensor or other component failure is detected. Production conventionally must remain stalled until maintenance can be performed on the failed or malfunctioning sensor. Production may cease for several hours until an operator replaces or repairs the faulty component(s).
A need therefore exists for an improved system for manufacturing products incorporating thermoplastic products.